swift - Swift 3 中 iOS 9 的核心数据不起作用

Question

我正在使用 XCode 8 开发一个具有核心数据功能的项目。 Xcode 8 确实支持 iOS 10 及更高版本的核心数据功能，但是当我尝试为 iOS 8 和 9 实现它时，它在获取带有消息的 managedContext 时崩溃:

fatal error: unexpectedly found nil while unwrapping an Optional value

代码:

让 managedContext = appDelegate.managedObjectContext

应用委托(delegate):

// MARK: - Core Data stack

@available(iOS 10.0, *)
lazy var persistentContainer: NSPersistentContainer = {
    /*
     The persistent container for the application. This implementation
     creates and returns a container, having loaded the store for the
     application to it. This property is optional since there are legitimate
     error conditions that could cause the creation of the store to fail.
     */
    let container = NSPersistentContainer(name: "Feel")
    container.loadPersistentStores(completionHandler: { (storeDescription, error) in
        if let error = error as NSError? {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.

            /*
             Typical reasons for an error here include:
             * The parent directory does not exist, cannot be created, or disallows writing.
             * The persistent store is not accessible, due to permissions or data protection when the device is locked.
             * The device is out of space.
             * The store could not be migrated to the current model version.
             Check the error message to determine what the actual problem was.
             */
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    })
    return container
}()


lazy var applicationDocumentsDirectory: URL = {

    let urls = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
    return urls[urls.count-1]
}()

lazy var managedObjectModel: NSManagedObjectModel = {
    // The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
    let modelURL = Bundle.main.url(forResource: "coreDataTemplate", withExtension: "momd")!
    return NSManagedObjectModel(contentsOf: modelURL)!
}()

lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
    // The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
    // Create the coordinator and store
    let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
    let url = self.applicationDocumentsDirectory.appendingPathComponent("SingleViewCoreData.sqlite")
    var failureReason = "There was an error creating or loading the application's saved data."
    do {
        try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url, options: nil)
    } catch {
        // Report any error we got.
        var dict = [String: AnyObject]()
        dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data" as AnyObject?
        dict[NSLocalizedFailureReasonErrorKey] = failureReason as AnyObject?

        dict[NSUnderlyingErrorKey] = error as NSError
        let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
        // Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
        abort()
    }

    return coordinator
}()

lazy var managedObjectContext: NSManagedObjectContext = {
    // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
    let coordinator = self.persistentStoreCoordinator
    var managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
    managedObjectContext.persistentStoreCoordinator = coordinator
    return managedObjectContext
}()


// MARK: - Core Data Saving support

func saveContext () {
    if #available(iOS 10.0, *) {

        let context = persistentContainer.viewContext
        if context.hasChanges {
            do {
                try context.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                fatalError("Unresolved error \(nserror), \(nserror.userInfo)")
            }
        }
    } else {
        if managedObjectContext.hasChanges {
            do {
                try managedObjectContext.save()
            } catch {
                // Replace this implementation with code to handle the error appropriately.
                // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
                let nserror = error as NSError
                NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
                abort()
            }
        }
    }
}

获取代码:

guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }

    if #available(iOS 10.0, *) {
        let managedContext =
            appDelegate.persistentContainer.viewContext

        let fetchRequest =
            NSFetchRequest<NSManagedObject>(entityName: "Test")

        do {
            tests = try managedContext.fetch(fetchRequest)
        } catch let error as NSError {
            print("Could not fetch. \(error), \(error.userInfo)")
        }
    } else {
        let appDelegate = UIApplication.shared.delegate as! AppDelegate
        let managedContext = appDelegate.managedObjectContext

        let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName: "Test")

        do {
            let results =
                try managedContext.fetch(fetchRequest)
            tests = results as! [NSManagedObject]
        } catch let error as NSError {
            print("Could not fetch \(error), \(error.userInfo)")
        }
    }

如何使用 Swift 3 在 XCode 8 中为部署版本为 iOS 8.2 的 iOS 项目实现核心数据？

Answer 1

您是否在 iOS 8/9 代码中使用了不同的型号名称？您能否尝试在 AppDelegate 的 managedObjectModel 属性中将 "coreDataTemplate" 替换为 "Feel"，如下所示:

let modelURL = Bundle.main.url(forResource: "Feel", withExtension: "momd")!